JPH071701B2 - Fuel cell assembly - Google Patents

Description

TECHNICAL FIELD The present invention relates to fuel cells, and more particularly to cooling systems for fuel cell stacks.

BACKGROUND OF THE INVENTION Electrochemical cells, such as fuel cells, consume reaction gases to produce reaction products, electricity and heat. This heat is a by-product of the electrochemical reaction. A cooling system is provided to remove this heat and maintain the temperature of the fuel cell at a temperature suitable for the characteristics of the material used therein to ensure the operating performance of the fuel cell.

An example of a cooling system used in a fuel cell is US Pat.
No. 245,009, No. 3,969,145, No. 4,233,369, No.
It is shown in No. 4,269,642.

U.S. Pat. No. 4,233,369 shows a cooler assembly disposed therein for cooling a fuel cell stack. In this case, the cooling fluid from one supply chamber is supplied to the cooler assembly by the supply pipe, and the cooling body is returned from the cooler assembly to the supply chamber via the return pipe. One inlet header is connected to the supply pipe, and one outlet header is connected to the return pipe. In each cooler assembly, a plurality of cooling tubes are provided in parallel between their inlet and outlet headers. Such a cooler assembly is housed in a groove that receives a cooling tube.

The electrical output of a fuel cell stack is increased by increasing the number of fuel cells. When the fuel cell is thus refined, the length of the stack increases. As the length of the fuel cell stack increases, the supply and return tubes for the cooler assembly increase. This increase in the length of the supply and return pipes increases the pressure loss of the cooling fluid flowing between the first header and the last header. By appropriately sizing the supply and return pipes, the overall pressure loss in these pipes can be made approximately equal. Longer lengths of these tubes result in different flow characteristics in each tube, or inhomogeneous pressure gradients in the region, or insufficient cooling fluid flow in the header, and cooling fluid flow in other headers. Becomes excessive. Such non-uniformity of the flow between the headers is recognized as a defective flow distribution. The defective distribution of the flow between the cooling parts is also caused by the difference in the heat load between the cooling parts, the difference in the fuel cell performance, the difference in the cross section of the flow path due to the deposits in the tubes, and the like. In addition, the poor flow distribution is caused by the difference in heat load between the tubes arranged in parallel even in one cooler, which causes the difference in fuel density in the cross-sectional direction of the fuel cell. .

One way to solve the problem of poor flow distribution is to increase the field resistance in the cooler assembly, i.e. the flow resistance between the supply and return pipes is controlled by the first header and the last header. The difference in flow resistance between the two increases insignificantly compared to the field resistance. To increase the flow resistance, for example, an orifice having a diameter smaller than the diameter of the tube may be provided. However, recent experience has included the problem that when using a cooling fluid such as water, the orifice tends to become clogged by the material dissolved therein depositing on the walls of the orifice. One solution to this is to remove any dissolved material or entrained particles during cooling. However, normalization of the cooling fluid is limited for economic or physical reasons.

It is therefore desirable to have a cooling system that is free from clogging problems, has no poor distribution of flow between each cooler assembly, and has minimal temperature changes in the fuel cell stack.

SUMMARY OF THE INVENTION In accordance with the present invention, a cooling system having a cooler assembly for a fuel cell assembly includes a supply pipe and a return pipe, and a plurality of pipes connecting these pipes to each other to conduct a cooling fluid. However, each of the tubes comprises a set of cooling tubes connected in series in series to form a serpentine passage for conducting cooling fluid through the cooler assembly.

A first feature of the present invention is a system having a plurality of cooler assemblies for removing heat from the fuel cell stack heat generating cells. The system has a supply line and a return line. Another feature of the present invention is a plurality of pipes connecting these supply pipes and return pipes. Each tube is located in the appropriate cooler assembly. Each tube consists of a set of cooling tubes. Each cooling tube extends across the fuel cell stack from one side of the cooler assembly to the other side. These pipes are connected to the supply pipe and the return pipe,
Connected in series with each other to form a tortuous path for the cooling fluid. One feature of the invention is the flow resistance of the conduit resulting from the nature of this tortuous path for the cooling fluid. The cooling system also has two sets of tubes. Each set of tubes has a set of cooling tubes alternating with one set of cooling tubes in the other set of tubes.

A first advantage of the present invention is to provide a cooling system capable of using a cooling fluid containing a foreign substance dissolved or suspended like water for a long period of time without causing failure of the cooling system. That is. This is due to the avoidance of the use of smaller diameter flow control orifices to avoid undesired poor distribution of the cooling fluid between each set of cooling tubes due to the flow resistance characteristics of the cooling tubes averaging the flow distribution. . In one embodiment, the advantage is that the header connected to the supply and cooling tubes and the connection between the header and the tube are eliminated and a single conduit with the tubes connected in series is used. It is in structural reliability and conciseness obtained by doing so. In one embodiment, the advantage resides in temperature gradients in the heat-producing fuel cell and cooler assembly tubes and uniformity in heat flow, which are interleaved and fluid flow in a counter-flow relationship. It is obtained by providing two conduits through which

The above features and advantages will be apparent from the description of the embodiments given below with reference to the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a portion of a fuel cell stack assembly 10. The assembly includes a fuel cell stack 12 and four reaction gas manifolds 14,16,18,20. Each reaction gas manifold covers each of the four sides of the fuel cell stack. Manifold 14 is an inlet manifold for fuel. Manifold 16 is an outlet manifold for fuel. Manifold 18 is the inlet manifold for the oxidant or air. Manifold 20 is the outlet manifold for the oxidant. These manifolds are pressed in a sealing relationship by a plurality of bands 22 against each side of the fuel cell stack.

The fuel cell stack assembly 10 includes a cooling system 24 that receives fluid from a fluid source not shown. This cooling system consists of a means for penetrating the cooling fluid and a supply pipe.
26, a return pipe 28, and a plurality of cooler assemblies, one of which is shown at 32. A plurality of conduits for cooling fluid extend between the supply and return tubes,
One of them is shown as tube 32. These tubes are regularly spaced along the length of the fuel cell stack, and their connections to the supply tubes are shown in dotted lines in FIG. Each tube is located within the appropriate cooler assembly.

FIG. 2 is a diagram showing in detail a part of the fuel cell stack assembly 10 according to the present invention. The fuel cell stack includes a plurality of fuel cells 34 assembled in a stack. A gas-tight separator plate 36 or cooler assembly 30 extends between each two fuel cells. Each cooler assembly has a gas-tight separator plate 36 ', which is the same as separator plate 36 and forms a gas-tight layer. In this embodiment, the plates 36, 36 'are 0.84 mm thick and have a length of about 50.8 cm and a width of about 50.8 cm.

The basic fuel cell structure is the same as shown and described in U.S. Pat. No. 4,115,627 owned by the applicant. Fuel cell 34 includes a thin matrix layer 38 for retaining the electrolyte. A negative electrode 42 is arranged on one side of the matrix layer and a positive electrode 44 is arranged on the other side. A phosphoric acid electrolyte is contained in the matrix between these negative and positive electrodes. It has a cathode substrate 46, which has a thickness of about 2.03 mm, is fibrous, porous and gas permeable. The substrate has a flat surface 48 facing the matrix layer 38. A thin catalyst layer (not shown) is provided on this surface. The catalyst layer is preferably 50.8 to 12.7 microns thick. The substrate has a second surface 52. A plurality of ribs 54 project from the second surface and are spaced apart from each other to provide a plurality of grooves 56 therebetween. These grooves extend across the entire fuel cell and fluidly connect the fuel inlet manifold 14 to the fuel outlet manifold 16.

The positive electrode 44 is similar in structure to the negative electrode. The positive electrode has a positive electrode substrate 58. A thin catalyst layer is provided on its surface 62, which is not shown in the figure. The positive electrode has a second surface 64. A plurality of ribs 66 project from the second surface, and these ribs are spaced apart from each other to form a plurality of grooves 68 therebetween. These grooves fluidly connect the air inlet manifold 18 to the air outlet manifold 20 and extend in a direction perpendicular to the fuel flow grooves in the cathode.

Each cooler assembly 30 has a plurality of grooves 72 extending therethrough.
And these grooves are adapted to receive the associated cooling tubes 102, 104.

The cooling system has first and second supply pipes 88,90 and first and second return pipes 92,94, through which the cooling fluid penetrates. They are connected by a first set of cooling pipes 102 that form a zigzag winding flow path. Also, the second supply pipe 90 and the second return pipe 94
Are also connected by a second set of cooling tubes 104.

By the way, the first supply pipe 88 is arranged adjacent to the second return pipe 94, and the first return pipe 92 is arranged adjacent to the second supply pipe 90. Further, the straight portions of the cooling pipes 102 and 104 of both sets are alternately housed in a plurality of parallel grooves 72 provided from each cooling assembly 30, and a second portion is provided next to the straight portions of the cooling pipes 102 of the first set. The straight portions of the cooling tubes 104 of the set are arranged. The cooling fluid inlet of the first set of cooling pipes 102 is connected to the first supply pipe 88, and the cooling fluid outlet thereof is connected to the first return pipe 92. Similarly, the cooling fluid inlet portion of the second set of cooling tubes 104 is connected to the second supply tube 90 located adjacent to the first return tube 92 and the cooling tubes 104
The cooling fluid outlet is connected to a second return pipe 94 located adjacent to the first supply pipe 88. In this way, the inlets of the first set of cooling tubes 102 are connected to the second set of cooling tubes 104.
Of the first set of cooling pipes 102 is adjacent to the outlet of the second set of cooling pipes 104. Thus, the cooling fluid flows in counterflow relation through these two conduits.

During operation of the fuel cell stack assembly 12, hydrogen (fuel)
And air (oxidizer) chemically combine in the fuel cell stack to generate electricity and heat. This heat transfers through the battery 34 to the cooler assembly 30. In this embodiment, the fuel cell stack has about 270 fuel cells, with every fifth of them having a cooler assembly. Cooling fluid is supply pipe 88,90
It passes through the cooler assembly in such a way that it flows through the cooling tubes 102, 104 towards the return tubes 92, 94. Heat is transferred to the cooling fluid flowing through the tubes within the cooler assembly. Each cooling tube has a diameter sufficient to carry the required flow rate of fluid as compared to other tubes placed in parallel with each other. The larger the flow rate of the cooling fluid and the larger the surface area of the cooling pipe, the larger the heat removal capacity of the cooling pipe. The flow resistance characteristics of this tortuous flow path are much higher than the flow resistance characteristics of the shorter tubes running in parallel. As a result, the field pressure drop from the inlet to the outlet of the conduit is higher than the pressure drop along the supply pipe,
This causes the amount of cooling fluid that each cooler assembly receives to be evenly divided. Of course, there is a difference in the flow rate of cooling fluid between each conduit, but the large amount of cooling fluid flowing through each conduit creates an undesirable distribution of defects between the amount of cooling fluid through each cooler assembly. Is avoided.

These cooling tubes may consist of individually made tubes connected together or may consist of a single long tube. In each case, the tube connections are greatly reduced compared to systems with conventional headers and parallel tubes connected between them. This also greatly reduces the possibility of leakage at the connection.

Moreover, in the operation of the cooling system, the cooling fluid is flowing in two different pipe systems in opposite directions. In this case, the temperature rise in one pipe system and the temperature rise in the other pipe system have an inverse relationship. This results in smaller temperature changes in the fuel cell stack.

It will be apparent to those skilled in the art that various modifications can be made to the embodiments described above within the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a perspective view showing a part of one fuel cell stack assembly, FIG. 2 is an enlarged view showing a part of the fuel cell stack assembly of the present invention, and FIG. 3 is a fuel cell of the present invention. It is a schematic diagram showing a cooler assembly of a stack. 10 …… Fuel cell stack assembly, 12 …… Fuel cell stack, 14,16,18,20 …… Gas manifold, 22 …… Band, 2
4 …… Cooler assembly, 26 …… Supply pipe, 28 …… Return pipe, 30
...... Cooler assembly, 32 …… Conduit, 34 …… Fuel cell, 36…
… Gas impermeable separator, 38 …… Matrix layer, 42 ……
Negative electrode, 44 …… Positive electrode, 46 …… Negative base material, 48 …… Matrix layer surface, 52 …… Base material surface, 54 …… Rib, 56 ……
Grooves, 58 ... Positive electrode base material, 84 ... Positive electrode surface, 66 ... Ribs,
68 groove, 72 …… groove, 88, 90 …… supply pipe, 92, 94 …… return pipe,
102, 104 ... Cooling tubes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-57-80677 (JP, A) JP-A-60-7066 (JP, A)

Claims (1)

[Claims] 1. A fuel cell assembly in which a plurality of fuel cells are stacked and assembled, the fuel cell assembly being disposed between a pair of fuel cells, one end of which is connected to a cooling fluid supply pipe and the other end of which is connected to a return pipe. It has a plurality of cooler assemblies equipped with two sets of cooling fluid flow devices consisting of zigzag cooling tubes, and the straight parts of both sets of cooling tubes in each cooler assembly are parallel to each other and alternate. Arranged so that the cooling fluid inlets of the first set of cooling tubes and the cooling fluid outlets of the second set of cooling tubes are adjacent to each other, and the cooling fluid outlets of the first set of cooling tubes And the cooling fluid inlets of the second set of cooling pipes are arranged adjacent to each other, and the cooling fluids flow in opposite directions in the cooling pipes of both sets. Battery assembly.